Time aligning loudspeaker drivers in a multi-driver system

This application is related to and claims priority to U.S. Provisional Application No. 63/478,259, filed Jan. 3, 2023, entitled TIME ALIGNING LOUDSPEAKER DRIVERS IN A MULTI-DRIVER SYSTEM, the entire contents of which is incorporated herein by reference.

This disclosure relates audio reproduction and in particular to a method and system for phase alignment of loudspeakers in audio systems.

Existing audio systems, e.g., for home theaters, vehicles, boats, etc., may include multiple speakers and associated audio drivers, such as subwoofer speakers, midbass speakers, midrange speakers, high-range speakers (tweeters), main speakers, etc. These speakers and/or audio drivers may be physically separated in space. Each of these speakers and/or audio drivers may be configured to produce audio within a respective frequency spectrum.

Existing systems may be configured for aligning the timing and/or phase of these multiple speakers, so that the playback on the speakers is time-aligned and/or phase-aligned in the ear of the listener. Existing systems typically utilize impulse responses for this purpose.

A “model” impulse response may define an ideal, target, and/or objectively correct and/or minimum phase difference/alignment between an example midbass and subwoofer speakers. For example, for some model impulse responses, the phase response of the subwoofer may seamlessly blend into the phase response of the midbass, i.e., there is no abrupt change in slope angle between the phase responses of the midbass and the subwoofer. For example, the target/model magnitude responses (also referred to as a “frequency response”) may include a crossover region where both subwoofer and midbass are active.

The magnitudes of the impulse responses may be controlled/adjusted/modified/etc. using equalizer (EQ) techniques. For example, a (measured) subwoofer impulse response may be equalized (EQd) so as to ensure proper response shape (e.g., to modify the shape of the measured impulse response to conform more closely to the shape of the model/target impulse response). As an example, ten EQ bands may be used for adjusting the frequency response so that it more closely matches the target response. Similarly, EQ filters may be applied to the measured midbass impulse response. The particular details of EQ algorithms are beyond the scope of the present disclosure. The target/model impulse response may be compared with measured impulse responses of subwoofer and midrange magnitude responses to determine accuracy.

Some existing systems perform a phase adjustment procedure which may suffer from various drawbacks.

For example, in some existing systems, delay finding methods (e.g., peak finder methods) only function properly under certain limited conditions. For example, the measured speaker may require significant high frequency energy, and the system may malfunction in the presence of room/environment-induced acoustic reflections. Thus, using conventional delay finders for aligning spectral crossovers may not function accurately or properly, especially where there is crossover, e.g., from the subwoofer and main system (e.g., in a studio setting), or where subwoofer/midbass crossovers occur (e.g., in active home or vehicle systems). Typically, this may result in inaccuracy of the measured delay values, which may be further compounded due to reflected energy in rooms, cars, etc.

For example, an example subwoofer impulse response and the midbass impulse response may be measured over time, where the peaks are measured by conventional delay finders. The measured peak for the subwoofer impulse response may be, as an example, 15.94 ms, and the measured peak for the midbass impulse response may be, as an example, 32.68 ms.

Existing systems for phase alignment may suffer from acoustic output being perceived (e.g., subjectively by a human listener) as degraded. Furthermore, existing systems may exhibit “seamlessness” in which the subwoofer “blends” with the main speakers (e.g., the midbass or other speakers). The magnitude response in dB and relative phase response in degrees are examples of objective mechanisms which may be used to assess whether an ideal alignment has been achieved.

Thus, existing systems may not be sufficient or accurate for adjusting the timing and/or phase relationship of two or more audio drivers and/or speakers.

Some embodiments advantageously provide a method and system for phase alignment in an audio system.

Some embodiments of the present disclosure may provide techniques for achieving a desired target timing/phase relationship between active drivers in a multiway/multi-speaker/multi-audio driver system. Just as equalizers are used to match the speakers' frequency response (e.g., the in-room response, the in-car response, etc.) to a target response, embodiments of the present disclosure may provide a target impulse response to correctly align the timing relationships between audio drivers.

According to a first aspect of the present disclosure, a method for phase alignment of audio signals using a first impulse response signal associated with a first frequency range and a second impulse response signal associated with a second frequency range is provided. The method includes determining a first start time for the first impulse response and a second start time for the second impulse response, determining a delay based at least in part on a difference between the second start time and the first start time, and adjusting at least one audio signal phase for a first audio driver operating in the first frequency range with respect to a second audio driver operating in the second frequency range, the adjusting of the at least one audio signal phase being based at least in part on the determined delay.

According to one or more embodiments of this aspect, the method further includes equalizing a magnitude of the first impulse response and a magnitude of the second impulse response prior to determining the delay.

According to one or more embodiments of this aspect, the delay is further determined based on a difference between the first start time and a reference start time of a model impulse response associated with at least one of the first frequency range and the second frequency range.

According to one or more embodiments of this aspect, the first frequency range is a subwoofer frequency range, and the second frequency range is a midrange frequency range.

According to one or more embodiments of this aspect, the method further includes generating a first reference audio signal associated with the first frequency range for playback on a first loudspeaker associated with the first audio driver and a second reference audio signal associated with the second frequency range for playback on a second loudspeaker associated with the second audio driver, and measuring the playback of the first loudspeaker to determine the first impulse response and measuring the playback of the second loudspeaker to determine the second impulse response.

According to one or more embodiments of this aspect, the determining of the first start time of the first impulse response signal includes determining a baseline noise level associated with the first frequency range, and detecting, at the first start time, a rise in the first impulse response signal over the baseline noise level, the rise being at least as large as a predetermined threshold value.

According to one or more embodiments of this aspect, the determining of the first start time of the first impulse response signal includes determining a baseline noise level associated with the first frequency range, and detecting, at the first start time, a rise in the first impulse response signal over the baseline noise level, the rise being at least as large as a predetermined threshold value.

According to another aspect of the present disclosure, a system for phase alignment of audio signals using a first impulse response signal associated with a first frequency range and a second impulse response signal associated with a second frequency range is provided. The system includes a calibration device configured to determine a first start time for the first impulse response and a second start time for the second impulse response, determine a delay based at least in part on a difference between the second start time and the first start time, and transmit a configuration to a receiver indicating the delay. The system further includes a receiver configured to receive the configuration from the calibration device, and responsive to receiving the configuration, adjust at least one audio signal phase for a first audio driver operating in the first frequency range with respect to a second audio driver operating in the second frequency range, the adjusting of the at least one audio signal phase being based at least in part on the delay.

According to one or more embodiments of this aspect, the calibration device is further configured to equalize a magnitude of the first impulse response and a magnitude of the second impulse response prior to determining the delay.

According to one or more embodiments of this aspect, the delay is further determined based on a difference between the first start time and a reference start time of a model impulse response associated with at least one of the first frequency range and the second frequency range.

According to one or more embodiments of this aspect, the first frequency range is a subwoofer frequency range, and the second frequency range is a midrange frequency range.

According to one or more embodiments of this aspect, the calibration device is further configured to generate a first reference audio signal associated with the first frequency range for playback on a first loudspeaker associated with the first audio driver and a second reference audio signal associated with the second frequency range for playback on a second loudspeaker associated with the second audio driver. The receiver is further configured to receive the first reference audio signal and the second reference audio signal, and cause playback of the first reference audio signal on the first loudspeaker and the second reference audio signal on the second loudspeaker. The calibration device is further configured to measure the playback of the first loudspeaker to determine the first impulse response, and measure the playback of the second loudspeaker to determine the second impulse response.

According to one or more embodiments of this aspect, the calibration device is further configured to determine the first start time of the first impulse response signal by determining a baseline noise level associated with the first frequency range, and detecting, at the first start time, a rise in the first impulse response signal over the baseline noise level, the rise being at least as large as a predetermined threshold value.

According to one or more embodiments of this aspect, the calibration device is configured to determine the first start time of the first impulse response signal by determining a baseline noise level associated with the first frequency range, and detecting, at the first start time, a rise in the first impulse response signal over the baseline noise level, the rise being at least as large as a predetermined threshold value.

According to another aspect of the present disclosure, a calibration device for phase alignment of audio signals using a first impulse response signal associated with a first frequency range and a second impulse response signal associated with a second frequency range is provided. The calibration device is configured to determine a first start time for the first impulse response and a second start time for the second impulse response, determine a delay based at least in part on a difference between the second start time and the first start time, and transmit a configuration to a receiver indicating the delay and enabling the receiver to adjust at least one audio signal phase for a first audio driver operating in the first frequency range with respect to a second audio driver operating in the second frequency range, the adjusting of the at least one audio signal phase being based at least in part on the delay.

According to one or more embodiments of this aspect, the calibration device is further configured to equalize a magnitude of the first impulse response and a magnitude of the second impulse response prior to determining the delay.

According to one or more embodiments of this aspect, the delay is further determined based on a difference between the first start time and a reference start time of a model impulse response associated with at least one of the first frequency range and the second frequency range.

According to one or more embodiments of this aspect, the first frequency range is a subwoofer frequency range, and the second frequency range is a midrange frequency range.

According to one or more embodiments of this aspect, the calibration device is further configured to generate a first reference audio signal associated with the first frequency range for playback a first loudspeaker associated with the first audio driver and a second reference audio signal associated with the second frequency range for playback on a second loudspeaker associated with the second audio driver, transmit the first reference audio signal and the second reference audio signal to the receiver enabling the receiver to cause playback of the first reference audio signal on the first loudspeaker and the second reference audio signal on the second loudspeaker, measure the playback of the first loudspeaker to determine the first impulse response, and measure the playback of the second loudspeaker to determine the second impulse response.

According to one or more embodiments of this aspect, the calibration device is configured to determine the first start time of the first impulse response signal by determining a baseline noise level associated with the first frequency range, and detecting, at the first start time, a rise in the first impulse response signal over the baseline noise level, the rise being at least as large as a predetermined threshold value.

Before describing in detail exemplary embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to phase alignment of loudspeakers in audio systems. Accordingly, the system and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In embodiments described herein, the joining term, “in communication with” and the like, may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example. One having ordinary skill in the art will appreciate that multiple components may interoperate and modifications and variations are possible of achieving the electrical and data communication.

1 FIG. 10 10 12 13 14 14 14 16 16 16 14 16 14 16 a n a n Referring again to the drawing figures in which like reference designators refer to like elements there is shown ina system designated generally as “.” Systemmay include a speaker systemlocated in a listening environment(e.g., a professional theater, home theater, vehicle cabin, boat cabin, etc.), which includes a plurality of speakers-(collectively, speakers) and a plurality of corresponding audio drivers-(collectively, audio drivers). In some embodiments, the speakersand audio driversare the same device, while in other embodiments, they may be separate devices, different modules within the same device, etc. Thus, as used herein, the term “speaker”, “loudspeaker”, and/or “audio driver” may be used interchangeably to refer to a speakerand/or audio driver.

14 14 14 12 14 14 a b 1 FIG. Speakermay be a subwoofer associated with a first frequency spectrum, while speakermay be a midbass associated with a second frequency spectrum. The first and second frequency spectra may be partially overlapping. Although only two speakers are shown in the example of, other speakers(e.g., tweeters, midrange, etc.) may be used in speaker system, such that the phases/delays of each of the speakersmay be calibrated to match one another and/or a reference speaker.

12 18 18 14 16 10 14 16 18 18 10 Speaker systemmay further include a receiverwhich is configured to receive and/or generate audio signals from one or more sources (e.g., digital media storage, internet-based streaming audio/video service, another device such as a smartphone, a calibration device, etc.). Receivermay transmit and/or receive analog and/or digital audio signals (and/or other signaling, such as data packets, audio channels, control signals, etc.) to/from speakersand/or audio drivers, or any other entity of system, via a wired and/or wireless (e.g., Bluetooth, Wi-Fi, etc.) channel and/or connection. Each speaker(and/or audio driver) may receive the audio signals from receiverat slightly different timings, e.g., due to differences in the wired and/or wireless connections (e.g., cable length, channel interference, random noise, hardware capabilities, etc.). Receivermay be configured to equalize audio signals and/or adjust the phases/timings of audio signals, e.g., according to a configuration received from another entity of system. Of note, although the invention is described with reference to a “receiver”, this is done purely for the sake of convenience and to aid understanding. Implementations are not limited to receiver in the audio/visual sense of a device with an integrated preamplifier, source selection components and amplifiers. Rather, “receiver” as used herein refers to the component that is receiving or generating audio signals intended for reproduction. Non-limiting examples include audio/visual receivers in the tradition sense, preamplifiers, digital signal processors, integrated amplifiers, and other computing devices that process signals for audio reproduction.

10 20 18 20 12 13 13 20 20 18 20 Systemfurther includes a calibration device, which may be configured to transmit and/or receive signaling (e.g., audio signals, data packets, control signals, etc.) to/from receiver, e.g., via a wired and/or wireless connection (e.g., Bluetooth, Wi-Fi, etc.). Calibration devicemay be a computing device configured for processing audio signaling and determining phase delay adjustments in a speaker system, which may be specifically calibrated for listening environmentor a particular location (e.g., the driver's seat in a car) in listening environment. For example, calibration devicemay be a portable computer, a stationary computer (e.g., desktop), a smartphone, a remote server, a cloud-based server, etc. In some embodiments, calibration devicemay be integrated with receiver, while in other embodiments, calibration devicemay be a separate device.

20 22 14 16 20 24 14 20 18 18 14 16 20 18 18 14 Calibration deviceincludes one or more microphonesfor detecting audio output from speakersand/or audio drivers. Calibration deviceincludes a calibration unitconfigured for detection of phase delay of speakersand/or for performing phase/timing calibration and alignment procedures, as disclosed herein. For example, calibration devicemay be configured to transmit (or indirectly cause transmission of, e.g., via an intermedia device and/or network) a configuration and/or control signaling to the receiverfor the receiverto apply to one or more audio signals/channels for speakersand/or audio drivers. For example, following a calibration procedure, as disclosed herein, calibration devicemay transmit to receiverconfiguration information which indicates one or more of a calibration metric, delay metric, phase/timing metric, etc., for receiverto apply to one or more audio signals/channels, e.g., for adjusting the phase of one or more audio signals/channels to align the timing/phase of a plurality of speakers.

20 2 FIG. Example implementations, in accordance with one or more embodiments, of calibration devicediscussed in the preceding paragraphs will now be described with reference to.

10 20 26 20 10 26 28 10 18 14 16 20 The systemincludes a calibration devicethat includes hardwareenabling the calibration deviceto communicate with one or more entities in systemand to perform one or more functions described herein. The hardwaremay include a communication interfacefor setting up and maintaining at least a wired and/or wireless connection to one or more entities in systemsuch as receiver, speakers, audio drivers, other calibration devices, etc.

26 20 30 30 32 34 30 32 34 In the embodiment shown, the hardwareof the calibration devicefurther includes processing circuitry. The processing circuitrymay include a processorand a memory. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitrymay comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or field programmable gate arrays (FPGAs) and/or application specific integrated circuits (ASICs) adapted to execute instructions. The processormay be configured to access (e.g., write to and/or read from) the memory, which may comprise any kind of volatile and/or nonvolatile memory, e.g., cache and/or buffer memory and/or random access memory (RAM) and/or read-only memory (ROM) and/or optical memory and/or erasable programmable read-only memory (EPROM).

20 36 34 20 36 30 30 20 32 32 20 34 36 32 30 32 30 20 30 20 24 20 Thus, the calibration devicefurther has softwarestored internally in, for example, memory, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the calibration devicevia an external connection. The softwaremay be executable by the processing circuitry. The processing circuitrymay be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by calibration device. Processorcorresponds to one or more processorsfor performing calibration devicefunctions described herein. The memoryis configured to store data, programmatic software code and/or other information described herein. In some embodiments, the softwaremay include instructions that, when executed by the processorand/or processing circuitry, causes the processorand/or processing circuitryto perform the processes described herein with respect to calibration device. For example, processing circuitryof the calibration devicemay include calibration unitwhich is configured to perform one or more calibration devicefunctions described herein such as with respect to phase delay detection and alignment procedures, as disclosed herein.

18 3 FIG. Example implementations, in accordance with one or more embodiments, of receiverdiscussed in the preceding paragraphs will now be described with reference to.

10 18 38 18 10 38 40 10 20 14 16 18 The systemincludes a receiverthat includes hardwareenabling the receiverto communicate with one or more entities in systemand to perform one or more functions described herein. The hardwaremay include a communication interfacefor setting up and maintaining at least a wired and/or wireless connection to one or more entities in systemsuch as calibration device, speakers, audio drivers, other receivers, etc.

38 18 42 42 44 46 42 44 46 In the embodiment shown, the hardwareof the receiverfurther includes processing circuitry. The processing circuitrymay include a processorand a memory. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitrymay comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or field programmable gate arrays (FPGAs) and/or application specific integrated circuits (ASICs) adapted to execute instructions. The processormay be configured to access (e.g., write to and/or read from) the memory, which may comprise any kind of volatile and/or nonvolatile memory, e.g., cache and/or buffer memory and/or random access memory (RAM) and/or read-only memory (ROM) and/or optical memory and/or erasable programmable read-only memory (EPROM).

18 48 46 18 48 42 42 18 44 32 18 46 48 44 42 44 42 18 42 18 25 18 14 16 20 Thus, the receiverfurther has softwarestored internally in, for example, memory, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the receivervia an external connection. The softwaremay be executable by the processing circuitry. The processing circuitrymay be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by receiver. Processorcorresponds to one or more processorsfor performing receiverfunctions described herein. The memoryis configured to store data, programmatic software code and/or other information described herein. In some embodiments, the softwaremay include instructions that, when executed by the processorand/or processing circuitry, causes the processorand/or processing circuitryto perform the processes described herein with respect to receiver. For example, processing circuitryof the receivermay include phase adjustment unitwhich is configured to perform one or more receiverfunctions described herein such as with respect to phase/timing alignment of audio signals for speakersand/or audio drivers(e.g., based on configuration information received from calibration device), as disclosed herein.

1 2 3 FIGS.,, and 24 25 Althoughshow calibration unitand phase adjustment unitas being within a respective processor, these units may be implemented such that a portion of a unit is stored in a corresponding memory within the processing circuitry. In other words, the units may be implemented in hardware or in a combination of hardware and software within the processing circuitry.

Embodiments of the present disclosure may provide methods, systems, and/or apparatuses for measuring phase delay of audio signals based at least in part on detecting the beginning/start of the measured impulse responses, e.g., when the signal emerges from the noise floor, which may yield an improved transient behavior (e.g., a more idealized impulse response shape), for example, as compared to conventional systems (e.g., systems which use peak alignment methods which determine the delay based on the magnitude peak of the impulse response) for impulse response phase delay measurement. Techniques based on detecting the beginning/start of the measured impulse responses may be referred to herein as “true delay” techniques. Some embodiments of the present disclosure using such true delay techniques may advantageously be less computationally expensive as compared to existing methods, e.g., existing methods where multiple computationally expensive fast Fourier transforms (FFTs) are required.

4 FIG. 5 FIG. 6 FIG. 4 FIG. 4 FIG. 5 FIG. 4 FIG. 6 FIG. 5 FIG. 6 FIG. 20 22 24 20 20 18 Initially it is noted that the discrete values provided herein are solely to aid understanding of the various embodiments.,, andillustrate an example phase alignment procedure according to embodiments of the present disclosure. In, example subwoofer impulse response and midbass impulse response are measured by calibration device(e.g., using microphone), and the start times of the impulse responses are determined (e.g., by calibration unit). This can be done, for example, by detecting the start times of the impulse responses. This may be in place of, or in addition to, conventional delay techniques, e.g., which measure the peak times of the impulse response signals. In the example of, the calibration device determines a 12.84 ms measured delay for the midbass impulse response and a 21.26 ms measured delay for the subwoofer impulse response. The longest measured delay time (21.26 ms in this example) is used by calibration deviceas the reference delay time, and the delta between the longest measured delay time and the other measured delay time(s) (in this example, the 12.84 ms delay time of the midbass channel) is determined, e.g., 8.42 ms, which may be considered the DSP delay. The calibration devicemay instruct receiverto insert the delta (e.g., 8.42 ms in this example) on the midbass channel (i.e., apply a timing/phase delay to the midbass channel(s) relative to the subwoofer channel(s)). The result of the phase adjustment using the calculated delta is illustrated in, which is a phase diagram which illustrates the result of applying the 8.42 ms calculated delta to the midbass impulse response of.illustrates the magnitude (frequency) response corresponding to the phase adjustment illustrated in. In, the subwoofer frequency response, midbass frequency response, summed frequency response, and target frequency response are shown. As a result of the phase adjustment procedure described above, according to embodiments of the present disclosure, there is reduced cancellation in the subwoofer region, which represents an improvement over conventional techniques (e.g., peak finder techniques).

6 FIG. Asshows, however, there may still be non-ideal alignment throughout the cross-over region in some examples. Additional processing according to some embodiments disclosed herein may achieve further improvement in phase alignment.

7 FIG. 8 FIG. 9 FIG. 7 FIG. 7 FIG. 8 FIG. 8 FIG. 9 FIG. 20 20 24 20 20 18 20 20 18 18 20 18 ,, andillustrate another example phase alignment procedure according to some embodiments of the present disclosure, in which a phase response of a model/target impulse response is used by calibration deviceas a calibration factor, which may be referred to herein as “calibrated true delay” embodiments or techniques.illustrates an example subwoofer impulse response, midrange impulse response, and target (model) impulse response. The timing difference between the measured subwoofer impulse response and the subwoofer model/target impulse response is determined by calibration device(e.g., via calibration unit). The model/target impulse response may be preconfigured in calibration device, and/or may be determined, e.g., based on the impulse response signal(s) which calibration deviceprovides to receiver. In the example of, the (measured) subwoofer impulse response delay time is measured as 21.26 ms, e.g., according to the techniques described above. The target impulse response delay time (e.g., a time corresponding to a point on the slope of the target impulse response which is the same as the slope of the measured impulse response at the measured impulse response delay time, as discussed below), is determined by calibration device(e.g., in this example, the target impulse response delay time is determined to be 2.89 ms). The calibrated true delay time is determined (e.g., by calibration deviceand/or receiver), based on the difference between the target impulse response delay time and the measured impulse response delay time (which in this example is 18.37 ms). This difference (e.g., 18.37 ms) is then used (e.g., by receiver) for adjusting the phase of the subwoofer audio signal and/or another audio signal/channel, as depicted in the example of. In, the delta (i.e., difference) between the target impulse response delay time and the measured impulse response delay time is added (e.g., by calibration deviceand/or receiver) to the subwoofer audio signal. The measured subwoofer curve, after the phase has been adjusted according to these above-described techniques, substantially overlays the target curve.depicts the improved alignment achieved according to embodiments of the present disclosure. The combined response matches closely to the ideal (model) summed target response.

20 20 20 20 18 The techniques as described herein (which may be referred to as “true delay” techniques and/or “calibrated true delay” techniques) may be superior to conventional techniques (e.g., peak finder techniques) in several ways. For example, embodiments of the present disclosure may determine a phase delay which may be robust even in the presence of acoustic reflections, and which may achieve more accurate delay time determinations than conventional techniques. For example, the peak of a subwoofer impulse response is often 10+ ms later than the actual initial arrival, and thus may be inaccurate as compared to measuring the start times of the impulse responses. Furthermore, as disclosed herein, using calibration factors (e.g., according to a calibrated true delay technique) for phase adjustment may further improve the accuracy of the phase adjustment by finding a point at the beginning of the target impulse response which is at least slightly up (or down) the slope of the measured impulse response signal. This may enable the calibration deviceto steer clear of (i.e., minimize the effects of, filter out, etc.) the noise floor in its determinations/calculations, which may aid in minimizing susceptibility to inaccurate and inconsistent results. By configuring the calibration deviceto apply the true delay algorithm to steer clear of the noise floor, calibration devicemay be able to improve consistency in accurately pinpointing (“locking onto”) a first point along the beginning slope of the impulse response(s) for use in determining the phase delay. The calibration devicemay then find a second point on the target/model impulse response, which may be the “same point” as the first point, e.g., with respect to the slopes of the acoustic impulse response and the model impulse response, and may determine the difference between the first point and the second point, where the difference is then used as a basis for determining the desired delay time and/or phase adjustment parameters) for the receiverto apply.

20 In some embodiments, the calibration devicemay determine at least one characteristic (e.g., the derivative, slope, etc.) of the measured impulse response(s) at the first point, and may determine/locate/identify the second point of the model impulse response based at least in part on the at least one characteristic of the first point. For example, the second point may be a point on the model impulse response which has similar or identical characteristic(s) (e.g., the same or similar slope(s) or derivative value(s)) compared to the characteristics of the measured impulse response at the first point.

20 20 In some embodiments, an example impulse response of the subwoofer when delay time is measured (by calibration device) using the true delay technique may be compared to the ideal (target/model) subwoofer impulse response. In some embodiments, an example impulse response of the subwoofer when the delay time is measured (by calibration device) using the calibrated true delay technique may be compared to the ideal (target/model) subwoofer impulse response. Such comparisons may enable determining the accuracy, improvement, etc., of the true delay technique and calibrated true delay technique.

In some embodiments, the subwoofer phase response and midbass phase response may be aligned using the true delay technique. In some embodiments, the subwoofer phase response and midbass phase response may be aligned using the calibrated true delay technique.

10 FIG. 11 FIG. 20 20 illustrates the subwoofer magnitude response, midbass magnitude response, summed magnitude response, and target magnitude response of example impulse response signals, where the delay time is measured by calibration deviceusing the true delay technique.illustrates the subwoofer magnitude response, midbass magnitude response, summed magnitude response, and target magnitude response of example impulse response signals, where the delay time is measured by calibration deviceusing the calibrated true delay technique. These figures illustrate and compare the improvement in accuracy, calibration, etc. provided by the true delay technique and calibrated true delay technique, as described herein.

20 14 In some embodiments, e.g., using a calibrated true delay technique, the calibration deviceconsiders the measured (“real”) impulse responses, and the target/model impulse responses. The difference in the two delay times may be the actual delay time of the subwoofer. Lower frequency range speakers, such as subwoofers, may in particular benefit from the techniques described herein, but it is to be understood that a variety of speaker types for different frequency spectra may be measured and calibrated/adjusted in this manner.

14 16 14 16 20 20 The calibrated true delay may result in more accurate phase adjustments, in particular when measuring lower frequency range speaker (e.g., subwoofer) delay times. In some embodiments, the lower in frequency the bandwidth (frequency spectrum associated with the speaker), the greater the accuracy improvement when using the calibrated true delay versus other techniques. Determining the start of the impulse responses using the true delay technique may work better for higher frequency transducer/speakers/audio drivers/etc., but for lower frequency speakers transducers/speakers/audio drivers/etc., the comparative model (e.g., calibrated true delay) may be utilized by calibration devicefor improved accuracy, where the comparative model describes the “actual” timing position of the subwoofer impulse response at “0 ms”, for example. Using a comparative model may also enable the determination by calibration deviceto steer clear of the noise floor, further improving accuracy/consistency/etc.

14 14 20 14 14 20 b a b a In some embodiments, the midbass speakerimpulse response and the subwoofer speakerimpulse response may be aligned by calibration devicevia the true delay technique, and the summed impulse responses may be compared to the ideal summed target impulse response. In some embodiments, the midbass speakerimpulse response and the subwoofer speakerimpulse response may be aligned by calibration devicevia the calibrated true delay technique, and the summed impulse responses may be compared to the ideal summed target impulse response.

14 14 20 14 14 20 b a b a In some embodiments, the phase responses of the midbass speakerimpulse response and the subwoofer speakerimpulse response may be aligned by calibration deviceusing the true delay technique. In some embodiments, the phase responses of the midbass speakerimpulse response and the subwoofer speakerimpulse response may be aligned by calibration deviceusing the calibrated true delay technique.

14 14 20 14 14 20 a b a b In some embodiments, the magnitude response of the subwoofer speakerimpulse response, the midbass speakerimpulse response, the summed measured impulse responses, and the target/model impulse response may be determined when the calibration deviceapplies the true delay technique. In some embodiments, the magnitude response of the subwoofer speakerimpulse response, the midbass speakerimpulse response, the summed measured impulse responses, and the target/model impulse response may be determined when the calibration deviceapplies the calibrated true delay technique.

14 14 20 14 b a Comparing the above examples, the calibrated true delay technique may typically result in a more accurate measured impulse response, a more minimized difference in phase angle between midbass speakerimpulse response and subwoofer speakerimpulse response, and a more optimal summation of individual responses, as compared with the true delay technique. In some embodiments, a calibrated true technique may include the calibration devicerunning the target/model impulse response through the true delay algorithm to determine a second delay value, and determining the delay time, and subtracting that from the first true delay value of the measured impulse response(s) to obtain the phase difference to be applied (the “actual delay” of the speaker).

20 14 14 20 b a In some embodiments, the summed impulse response may be compared to the target impulse response when aligned by calibration deviceusing a true delay technique according to some embodiments of the present disclosure. In some embodiments, the phase responses of the midbass speakerimpulse response and the subwoofer speakerimpulse response may be compared when aligned by calibration deviceusing the true delay technique.

20 14 14 20 b a In some embodiments, the summed impulse response may be compared to the target impulse response when aligned by calibration deviceusing a calibrated true delay technique according to some embodiments of the present disclosure. In some embodiments, the phase responses of the midbass speakerimpulse response and the subwoofer speakerimpulse response may be compared when aligned by calibration deviceusing the calibrated true delay technique.

In some embodiments, the acoustic amplitude may be determined as a function of time. In some embodiments, the phase may be determined as a function of frequency.

12 FIG. 10 18 20 20 22 28 30 24 32 18 40 42 25 44 20 100 20 102 20 104 20 18 104 20 is a flowchart of an example process in a systemincluding a receiverand a calibration deviceaccording to one or more embodiments of the present invention. One or more blocks described herein may be performed by one or more elements of calibration devicesuch as by one or more of microphone, communication interface, processing circuitry(including the calibration unit), processor, etc. One or more blocks described herein may be performed by one or more elements of receiversuch as by one or more of communication interface, processing circuitry(including the phase adjustment unit), processor, etc. Calibration deviceconfigured to determine (Block S) a first start time for the first impulse response and a second start time for the second impulse response. Calibration deviceconfigured to determine (Block S) a delay based at least in part on a difference between the second start time and the first start time. Calibration deviceis configured to transmit (Block S) of a configuration to a receiver indicating the delay. In some embodiments, calibration deviceand receivermay be the same device, in which case, the transmission (Block S) may not occur, and/or may occur within the device (e.g., between different modules, processors, etc.). In some embodiments, the configuration may indicate and/or include the delay (and/or one or more values/parameters/metrics which are determined/detected by calibration device).

18 106 18 108 Receiveris configured to receive (Block S) the configuration from the calibration device. Receiveris configured to, responsive to receiving the configuration, adjust (Block S) at least one audio signal phase for a first audio driver operating in the first frequency range with respect to a second audio driver operating in the second frequency range, where the adjusting of the at least one audio signal phase is based at least in part on the delay (and/or other metrics/values indicated by the configuration).

20 18 20 18 20 18 In some embodiments, the calibration device(and/or the receiver) is further configured to equalize the magnitudes of the first impulse response and the second impulse response prior to determining the delay. In some embodiments, the calibration device(and/or the receiver) is further configured to determine the delay based on a difference between the first start time (i.e., of the measured “real” acoustic response) and a reference start time of a model impulse response (i.e., a mathematically generated, pure signal w/o noise, where the model impulse response is run through the a delay finder procedure at the same settings/parameters as the measured impulse response(s) to determine the reference start time) associated with at least one of the first frequency range and the second frequency range. The model impulse response may be generated by calibration deviceand/or receiver, and/or may be preconfigured. In some embodiments, the first frequency range is a subwoofer frequency range, and the second frequency range is a midrange frequency range.

18 20 14 14 20 14 14 a b a b In some embodiments, receiveris further configured to generate (and/or receive, e.g., from another device, such as calibration device) a first reference audio signal associated with the first frequency range for playback on the first loudspeakerand a second reference audio signal associated with the second frequency range for playback on the second loudspeaker. The calibration deviceis further configured to measure the playback of the first loudspeakerto determine the first impulse response, and measure the playback of the second loudspeakerto determine the second impulse response.

In some embodiments, the determining of the first start time of the first impulse response signal includes determining a baseline noise level (e.g., one or more of a baseline ambient noise level, an acoustic noise floor, Gaussian white noise, etc.) associated with the first frequency range, and detecting, at the first start time, a rise in the first impulse response signal over the baseline signal level, the rise being at least as large as a predetermined (and/or preconfigured) threshold value.

20 14 16 14 16 18 14 14 20 14 14 In some embodiments, the calibration deviceis further configured to generate a first reference audio signal associated with the first frequency range for playback on a first loudspeakerassociated with the first audio driverand a second reference audio signal associated with the second frequency range for playback on a second loudspeakerassociated with the second audio driver. The receiveris further configured to receive the first reference audio signal and the second reference audio signal, and cause playback of the first reference audio signal on the first loudspeakerand the second reference audio signal on the second loudspeaker. The calibration deviceis further configured to measure the playback of the first loudspeakerto determine the first impulse response, and measure the playback of the second loudspeakerto determine the second impulse response.

20 In some embodiments, the calibration deviceis further configured to determine the first start time of the first impulse response signal by determining a baseline noise level associated with the first frequency range, and detecting, at the first start time, a rise in the first impulse response signal over the baseline noise level, the rise being at least as large as a predetermined threshold value.

13 FIG. 20 20 22 28 30 24 32 20 110 112 114 18 16 16 is a flowchart of an example process in a calibration deviceaccording to one or more embodiments of the present invention. One or more blocks described herein may be performed by one or more elements of calibration devicesuch as by one or more of microphone, communication interface, processing circuitry(including the calibration unit), processor, etc. Calibration deviceconfigured to determine (Block S) a first start time for the first impulse response and a second start time for the second impulse response, determine (Block S) a delay based at least in part on a difference between the second start time and the first start time, and transmit (Block S) a configuration to a receiverindicating the delay and enabling the receiver to adjust at least one audio signal phase for a first audio driveroperating in the first frequency range with respect to a second audio driveroperating in the second frequency range, the adjusting of the at least one audio signal phase being based at least in part on the delay.

20 In some embodiments, the calibration deviceis further configured to equalize a magnitude of the first impulse response and a magnitude of the second impulse response prior to determining the delay.

In some embodiments, the delay is further determined based on a difference between the first start time and a reference start time of a model impulse response associated with at least one of the first frequency range and the second frequency range.

In some embodiments, the first frequency range is a subwoofer frequency range, and the second frequency range is a midrange frequency range.

20 14 16 14 16 18 18 14 14 14 14 In some embodiments, the calibration deviceis further configured to generate a first reference audio signal associated with the first frequency range for playback a first loudspeakerassociated with the first audio driverand a second reference audio signal associated with the second frequency range for playback on a second loudspeakerassociated with the second audio driver, transmit the first reference audio signal and the second reference audio signal to the receiverenabling the receiverto cause playback of the first reference audio signal on the first loudspeakerand the second reference audio signal on the second loudspeaker, measure the playback of the first loudspeakerto determine the first impulse response, and measure the playback of the second loudspeakerto determine the second impulse response.

18 According to one or more embodiments of this aspect, the calibration deviceis configured to determine the first start time of the first impulse response signal by determining a baseline noise level associated with the first frequency range, and detecting, at the first start time, a rise in the first impulse response signal over the baseline noise level, the rise being at least as large as a predetermined threshold value.

determining a first start time for the first impulse response and a second start time for the second impulse response; determining a delay based at least in part on a difference between the second start time and the first start time; and adjusting at least one audio signal phase for a first audio driver operating in the first frequency range with respect to a second audio driver operating in the second frequency range, the adjusting of the at least one audio signal phase being based at least in part on the determined delay. Example A1. A method for phase alignment of audio signals using a first impulse response signal associated with a first frequency range and a second impulse response signal associated with a second frequency range, the method comprising:

equalizing the magnitudes of the first impulse response and the second impulse response prior to determining the delay. Example A2. The method of Example A1, wherein the method further comprises:

Example A3. The method of any one of Examples A1 and A2, wherein the delay is further determined based on a difference between the first start time and a reference start time of a model impulse response associated with at least one of the first frequency range and the second frequency range.

Example A4. The method of any one of Examples A1-A3, wherein the first frequency range is a subwoofer frequency range, and the second frequency range is a midrange frequency range.

14 14 generating a first reference audio signal associated with the first frequency range for playback on the first loudspeakerand a second reference audio signal associated with the second frequency range for playback on the second loudspeaker; and 14 14 measuring the playback of the first loudspeakerto determine the first impulse response and measuring the playback of the second loudspeakerto determine the second impulse response. Example A5. The method of any one of Examples A1-A4, wherein the method further comprises:

determining a baseline noise level (i.e., baseline ambient noise level, acoustic noise floor, etc.) associated with the first frequency range; and detecting, at the first start time, a rise in the first impulse response signal over the baseline signal level, the rise being at least as large as a predetermined threshold value. Example A6. The method of any one of Examples A1-A5, wherein the determining of the first start time of the first impulse response signal includes:

10 20 20 30 determine a first start time for the first impulse response and a second start time for the second impulse response; determine a delay based at least in part on a difference between the second start time and the first start time; 18 cause transmission of a configuration to a receiverindicating the delay; a calibration device, the calibration devicecomprising processing circuitryconfigured to: 18 18 42 20 receive the configuration from the calibration device; and 16 16 responsive to receiving the configuration, adjust at least one audio signal phase for a first audio driveroperating in the first frequency range with respect to a second audio driveroperating in the second frequency range, the adjusting of the at least one audio signal phase being based at least in part on the delay. a receiver, the receivercomprising processing circuitryconfigured to: Example B1. A systemfor phase alignment of audio signals using a first impulse response signal associated with a first frequency range and a second impulse response signal associated with a second frequency range, the system comprising:

10 30 equalize the magnitudes of the first impulse response and the second impulse response prior to determining the delay. Example B2. The systemof Example B1, wherein the processing circuitryof the calibration device is further configured to:

10 Example B3. The systemof any one of Examples B1 and B2, wherein the delay is further determined based on a difference between the first start time and a reference start time of a model impulse response associated with at least one of the first frequency range and the second frequency range.

10 Example B4. The systemof any one of Examples B1-B3, wherein the first frequency range is a subwoofer frequency range, and the second frequency range is a midrange frequency range.

10 42 18 14 14 generate and/or receive a first reference audio signal associated with the first frequency range for playback on the first loudspeakerand a second reference audio signal associated with the second frequency range for playback on the second loudspeaker; and the processing circuitryof the receiveris further configured to: 30 20 14 measure the playback of the first loudspeakerto determine the first impulse response; and 14 measure the playback of the second loudspeakerto determine the second impulse response. the processing circuitryof the calibration deviceis further configured to: Example B5. The systemof any one of Examples B1-B4, wherein:

10 determining a baseline noise level (i.e., baseline ambient noise level, acoustic noise floor, etc.) associated with the first frequency range; and detecting, at the first start time, a rise in the first impulse response signal over the baseline signal level, the rise being at least as large as a predetermined threshold value. Example B6. The systemof any one of Examples B1-B5, wherein the determining of the first start time of the first impulse response signal includes:

It will be appreciated by persons skilled in the art that the present embodiments are not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings and the following claims.